Peeing blood bladder infection. What are clinical trials, and are they right for you? A blow or other injury to your kidneys from an accident or contact sports can cause visible blood in your urine. What clinical trials are open? Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. If two of three urine samples detect too many red blood cells, a health care professional may order one or more additional tests. Important Blood in urine must be checked out because it can be a sign of cancer. Long-distance runners are especially prone to exercise-induced urinary bleeding. Changes in bladder habits or symptoms of irritation Bladder cancer can sometimes cause changes in urination, such as: If there's a reason to suspect you might have submit your licks cancer, the doctor will use one or more exams or tests to find out if it's cancer or something else. If you see blood in your urine after exercise, don't assume it's from exercising. The treatment for having blood in your urine depends on what is causing the problem.